PEMFC 전극촉매 Pt/C와 PtCo/C의 촉매 지지체 열화비교

오소형,한유한,정민철,유동근,박권필,Sohyeong Oh,Yoohan Han,Minchul Chung,Donggeun Yoo,Kwonpil Park 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

In PEMFC, PtCo/C alloy catalysts are widely used because of good performance and durability. However, few studies have been reported on the durability of carbon supports of PtCo/C evaluated at high voltages (1.0~1.5 V). In this study, the durability of PtCo/C catalysts and Pt/C catalysts were compared after applying the accelerated degradation protocol of catalyst support. After repeating the 1.0↔1.5V voltage change cycles, the mass activity, electrochemical surface area (ECSA), electric double layer capacitance (DLC), Pt dissolution and the particle growth were analyzed. After 2,000 cycles of voltage change, the current density per catalyst mass at 0.9V decreased by more than 1.5 times compared to the Pt/C catalyst. This result was because the degradation rate of the carbon support of the PtCo/C catalyst was higher than that of the Pt/C catalyst. The Pt/C catalyst showed more than 1.5 times higher ECSA reduction than the PtCo/C catalyst, but the corrosion of the carbon support of the Pt/C catalyst was small, resulting in a small decrease in I-V performance. In order to improve the high voltage durability of the PtCo/C catalyst, it was shown that improving the durability of the carbon support is essential.

고분자전해질 연료전지에서 박막의 화학적 내구성 평가

오소형,유동근,정성기,정지홍,박권필,Sohyeong Oh,Donggeun Yoo,Sunggi Jung,Jihong Jeong,Kwonpil Park 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

PEMFC 고분자 막의 전기화학적 가속 열화에 미치는 평가조건들의 영향

오소형,유동근,배석주,채선규,박권필,Sohyeong Oh,Donggeun Yoo,Suk Joo Bae,Sun Geu Chae,Kwonpil Park 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

In order to improve the durability of the proton exchange membrane fuel cell (PEMFC), it is important to accurately evaluate the durability of the polymer membrane in a short time. The test conditions for chemically accelerated durability evaluation of membranes are high voltage, high temperature, low humidity, and high gas pressure. It can be said that the protocol is developed by changing these conditions. However, the relative influence of each test condition on the degradation of the membrane has not been studied. In chemical accelerated degradation experiment of the membrane, the influence of 4 factors (conditions) was examined through the factor experiment method. The degree of degradation of the membrane after accelerated degradation was determined by measuring the hydrogen permeability and effluent fluoride ion concentration, and it was possible to determine the degradation order of the polymer membrane under 8 conditions by the difference in fluoride ion concentration. It was shown that the influence of the membrane degradation factor was in the order of voltage > temperature > oxygen pressure > humidity. It was confirmed that the degradation of the electrode catalyst had an effect on the chemical degradation of the membrane.

PEMFC Cathode 산소 조건에서 전극 촉매 내구성 평가

오소형 ( Sohyeong Oh ),임대현 ( Daehyeon Lim ),박권필 ( Kwonpil Park ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.1

본 연구에서는 전극촉매 내구성 평가를 potentiostat를 사용하지 않고 간단히 로더(Electronic loader)를 사용해 전극을 가속 열화시키는 방법을 개발하고자 하였다. 이를 위해, cathode에 질소를 유입하지 않고 산소를 유입해 자체 발생 전압을 활용해서 계단식 전압변화를 반복해 전극의 내구성을 평가하였다. 정확한 전극 내구평가를 위해 즉 고분자 막이 열화되지 않게 하기 위해 계단식 전압변화에서 고전압은 0.9 V로 낮게하고, 상대습도를 100%하여 라디칼에 의한 고분자 막 열화를 억제하고자 하였다. 전압변화 30,000 cycle (50시간) 만에 전극활성면적이 41.4% 감소했다. 전극은 열화되지만 고분자 막이 열화되지 않음을 수소투과도 증가가 없고 막 두께감소 없으면서 HFR (High Frequency Resistance)증가 없는 것으로 확인했다. In this study, we tried to develop a method of accelerated degradation of the electrode by simply using a electronic loader without using a potentiostat to evaluate the durability of the electrode catalyst. To this end, the durability of the electrode was evaluated by repeating the stepwise voltage change using the self-generated voltage by introducing oxygen without introducing nitrogen into the cathode. For accurate electrode durability evaluation, that is, in order not to deteriorate the polymer membrane, the high voltage was lowered to 0.9 V in stepwise voltage change and the relative humidity was 100% to suppress degradation of the polymer membrane due to radicals. After 30,000 cycles (50 hours) of voltage change, the electrode active area decreased by 41.4%. It was confirmed that the electrode was deteriorated, but the polymer membrane was not deteriorated, that there was no increase in hydrogen permeability, no decrease in membrane thickness, and no increase in HFR(High Frequency Resistance).

순수 수소 공급조건에서 정치용 PEMFC MEA와 차량용 MEA 성능비교

오소형,이미화,이학주,김욱원,박정우,박권필,Oh, Sohyeong,Lee, Mihwa,Lee, Hakju,Kim, Wookwon,Park, Jeong-Woo,Park, Kwonpil 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.4

개질가스를 일반적으로 사용하는 정치용 PEMFC에 순수 수소를 공급했을 때 그 특성을 차량용 막과 전극 합체(MEA)와 비교하였다. 수소 공급량을 변화시키며 anode에서 수소공급량이 전체 성능에 미치는 영향을 비교하였다. 수소를 1.0~1.7 과잉(stoi.)범위에서 공급량을 변화시켰을 때 정치용이나 차량용 모두 OCV에 미치는 영향은 거의 없었다. 0.7 V에서 정치용 MEA의 전류밀도는 차량용보다 약 16% 높았다. 그리고 상대습도를 변화시키며 I-V 성능, 임피던스, LSV를 측정하였다. 상대습도 증가에 따라 OCV와 전해질 막 저항이 모두 감소하였다. 정치용 MEA의 수소투과도가 차량용보다 더 낮아 정치용 MEA의 전해질 막의 내구성이 차량용보다 더 높을 수 있음을 보였다. When pure hydrogen was supplied to the stationary PEMFC generally using the reforming gas, its characteristics were compared with the vehicle PEMFC. The effect of varying the amount of hydrogen supply to the anode on the overall performance was compared. The variation of hydrogen supply in the range of 1.0~1.7 excess (stoi.) had little effect on the OCV of stationary and vehicle MEA (Membrane and Electrode Assembly). At 0.7 V, the current density of the stationary MEA was about 16% higher than that of the vehicle MEA. I-V performance, impedance, and LSV were measured with varying relative humidity. Both OCV and electrolyte membrane resistances decreased with increasing relative humidity. The hydrogen permeability of the stationary MEA was lower than that of the vehicle MEA, showing that the durability of the stationary membrane could be higher than that of the vehicle membrane.

철-크롬 산화환원흐름전지에서 Nafion막의 철-크롬 Crossover

김영숙,오소형,김은비,김다영,김성지,추천호,박권필,Kim, Young-Sook,Oh, So-Hyeong,Kim, Eunbi,Kim, Dayoung,Kim, Seongji,Chu, Cheun-Ho,Park, Kwonpil 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.1

산화환원흐름전지(Redox Flow Battery, RFB)는 대용량 에너지 저장장치로 바나듐 산화환원흐름전지가 대표적인 RFB인데, VRFB는 고가인 점이 문제다. 철-크롬RFB는 저가의 활물질을 사용해 경제적인 점이 장점인데, 성능이 낮은 점이 해결해야할 과제다. 낮은 성능의 한 원인이 활물질의 크로스오버인데, 본 연구에서 철과 크롬 이온의 Nafion 막 크로스오버 및 Nafion 막의 안정성에 대해 실험하였다. 철과 크롬이온의 Nafion 막 투과도는 각각 $5.5{\times}10^{-5}$, $6.0{\times}10^{-5}cm^2/min$ 이었다. Nafion 막에서 바나듐 이온의 투과도 $2.9{\times}10^{-6}cm^2/min$ 보다 18.9~20.7배 높아 철과 크롬 이온의 Nafion 막 크로스오버가 성능 저하의 한 원인임을 보였다. 온도 증가에 따라 크로스오버가 급증(활성화 에너지 38.8 kJ/mol)하므로 낮은 온도에서 구동하는 것이 크로스오버에 의한 성능감소를 저하시키는 방법임을 나타냈다. Nafion막은 3M HCl용액에서 비교적 안정적이었다. The redox flow battery (RFB) is a large-capacity energy storage equipment, and the vanadium redox flow cell is a typical RFB, but VRFB is expensive. Iron-chrome RFBs are economical because they use low-cost active materials, but their low performance is a urgent problem. In this study, the crossover of iron and chromium ion through Nafion membrane and the stability of Nafion membrane in HCl solution were investigated. The permeability of iron and chrome ion through Nafion were $5.5{\times}10^{-5}$ and $6.0{\times}10^{-5}cm^2/min$, respectively, which was 18.9~20.7 times higher than that of vanadium ion ($2.9{\times}10^{-6}cm^2/min$). The crossover of iron and chromium ions were shown to be a cause of performance decrease in Iron-chrome RFB. As the temperature increases, the crossover increases rapidly (activation energy 38.8 kJ/ mol), indicating that operation at low temperature is a methode to reduce the performance loss due to crossover. Nafion membranes were relatively stable in 3 M HCl solution.

고분자 전해질 연료전지의 전해질 막 두께가 내구성과 성능에 미치는 영향

황병찬 ( Byungchan Hwang ),이혜리 ( Hyeri Lee ),박권필 ( Kwonpil Park ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.4

고분자 전해질 연료전지(PEMFC)의 고분자 막은 PEMFC 성능과 내구성에 많은 영향을 준다. 본 연구에서는 고분자막의 두께가 성능과 내구성에 미치는 영향을 파악하기 위해 두께가 다른 Nafion 막의 수소투과도, 불소 유출 속도(FER), 수명, 성능을 측정했다. 막 두께에 따른 수소투과도, 수소투과도와 FER과의 관계, FER과 수명과의 관계로부터 막 두께와 수명의 관계를 얻었다. 막이 두꺼워지면 수소투과도와 FER이 작아지면서 수명이 증가하였다. 반면에 막이 두꺼워지면 막 저항이 증가하면서 성능은 감소하였다. 성능과 내구성을 동시에 만족시키는 막 두께 범위는 25~28 μm 였다. The polymer membrane of proton exchange membrane fuel cell (PEMFC) has a great influence on PEMFC performance and durability. In this study, hydrogen permeability, fluorine emission rate (FER), lifetime, and performance of Nafion membranes with different thicknesses were measured to investigate the effect of thickness of polymer membrane on performance and durability. The relationship between membrane thickness and lifetime was obtained from the relationships between hydrogen permeability and membrane thickness, hydrogen permeability and FER, FER and lifetime. As the membrane became thicker, the hydrogen permeability and FER decreased and the lifetime increased. On the other hand, the performance decreased with increasing membrane resistance. The membrane thickness range satisfying both performance and durability was 25 to 28 μm.

고분자전해질 연료전지 고분자막의 특성 및 성능 비교

이대웅,오소형,임대현,정회범,유승을,구영모,박권필,Lee, Daewoong,Lim, Daehyun,Oh, Sohyeong,Chung, Hoi-Bum,Yoo, Seung-Eul,Ku, Young-Mo,Park, Kwonpil 한국화학공학회 2020 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.58 No.2

In the proton exchange membrane fuel cells (PEMFC), the development of a reinforced membrane with improved durability by a support is actively in progress in Korea. In this study, the initial performance and characteristics of four types of reinforced membranes were compared. Reinforced membranes with higher amounts of C-F chains in the polymer membrane showed lower water diffusion coefficients due to the hydrophobicity of the C-F chains. The thicker the polymer membrane, the more the hydrogen permeability decreased and the higher the OCV. Membrane with short resistance below 1.5 Ωcm² showed OCV below 0.9 V and the lowest performance, so short resistance should be above 3.0 Ωcm². Compared with the current standard membrane, there was a similar domestic membrane, which could confirm the possibility of localization of PEMFC polymer membrane. 고분자전해질 연료전지(PEMFC)에서 지지체에 의해 내구성을 향상시킨 강화막(Reinforced Membrane)의 개발이 국내에서 활발히 진행되고 있다. 본 연구에서는 4 종류의 강화막의 초기 성능 및 특성을 비교하였다. 고분자막의 C-F사슬의 양이 더 많은 강화막이 C-F사슬의 소수성 때문에 물 확산계수가 더 작음을 보였다. 고분자막 두께가 두꺼울수록 수소투과도가 감소하고 OCV가 증가함을 확인하였다. Short 저항이 1.5 Ωcm² 이하인 막은 OCV가 0.9 V이하이고 성능도 최저여서 Short 저항이 3.0 Ωcm² 이상이어야 함을 보였다. 현재 기준이 되는 국외 막과 비교했을 때 비슷한 국내 막도 있어서 PEMFC 고분자막의 국산화 가능성을 확인할 수 있었다.

PEMFC 고분자막의 화학적 내구성 평가를 위한 Fenton 반응 조건에 관한 연구

오소형 ( Sohyeong Oh ),박지상 ( Jisang Park ),정성기 ( Sunggi Jung ),정지홍 ( Jihong Jeong ),박권필 ( Kwonpil Park ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.1

고분자 연료전지(PEMFC) 고분자막의 화학적 내구성을 평가하는데 Fenton 반응이 자주 사용된다. 그러나 과산화수소와 철 이온의 격렬한 반응 때문에 재현성이 낮아 실험 데이터를 비교하기가 어려운 문제점이 있다. 본 연구에서는 Fenton 반응에 의한 고분자막 내구성 실험의 재현성을 향상시키기 위한 반응조건을 찾고자 하였다. 과산화수소 농도는 30%로 고정시키고 철이온 농도와 온도, 교반속도, 시료크기를 변화시키며 라디칼에 열화된 Nafion 고분자막의 불소이온 농도를 측정했다. 철이온 농도를 높게하거나 고분자막 시료 크기를 크게하고, Fenton 반응 온도를 80 ℃로 높게하면 실험편차가 커져서 철이온 농도 10 ppm, 온도 70℃와 시료크기 0.5 cm²가 적합하였다. The Fenton reaction is often used to evaluate the chemical durability of polymer membranes of Proton Exchange Membrane Fuel Cells (PEMFC). However, due to the violent reaction between hydrogen peroxide and iron ions, it is difficult to compare experimental data because of low reproducibility. In this study, we tried to find the reaction conditions to improve the reproducibility of the durability test of the membrane by the Fenton reaction. The hydrogen peroxide concentration was fixed at 30%, the iron ion concentration, temperature, stirring speed, and sample size were varied, and the fluorine ion concentration of the Nafion polymer membrane deteriorated by radicals was measured. When the iron ion concentration was increased or the membrane sample size was increased, and the reaction temperature was increased to 80℃, the experimental deviation increased, so an iron ion concentration of 10 ppm, a temperature of 70℃, and a sample size of 0.5 cm² were suitable.

고분자 전해질 연료전지 구동 조건에 따른 MEA 열화 및 배출수 특성

황병찬 ( Byungchan Hwang ),이세훈 ( Sehoon Lee ),나일채 ( Il-chai Na ),박권필 ( Kwonpil Park ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.4

고분자 전해질 연료전지의 구동과정 중 습도제어는 매우 중요한 제어 조건이다. 물 관리 측면에서는 저가습 조건이 유리하고, 배출수 활용 및 에너지 효율면에서는 고가습이 유리하다. 본 연구에서는 배출수 활용면에서 저가습과 고가습 구동 과정에서 배출수의 특성에 대해서 연구하였다. 배출수의 불순물은 막과 전극의 열화 과정에서 발생하는 것이므로 저가습과 고가습 조건에서 막전극합체(MEA)열화에 대해서도 연구하였다. 연료극 0% RH의 저가습 조건에서 라디칼 발생속도가 커 고분자 막 열화의 주요 원인임을 보였다. 양쪽 극 모두 고가습(RH 100%) 0.6 V에서 불소 이온 농도 약20 ppb로 낮은 농도를 나타내서, 수전해 원료수로 사용하기에 충분하였다. 고가습 조건에서 배출한 응축수에서 0.2 ppb이하의 매우 낮은 농도의 백금이 검출되었다. Humidity control of proton exchange membrane fuel cell(PEMFC) is very important control condition during driving. In terms of water management, low humidification conditions are advantageous, and high humidification is advantageous in terms of drainage utilization and energy efficiency. In this study, the characteristics of outlet water in low humidification and high humidification process were studied in terms of utilization of discharged water. Since the impurities in the effluent are generated during the degradation of the membrane and the electrode assembly( MEA), degradation of the MEA under low humidification and high humidification conditions was also studied. The rate of radical generation was high at low humidification condition of the anode RH 0%, which showed that it was the main cause of the degradation of the polymer membrane. Analysis of effluent showed low concentration of fluoride ion concentration of about 20 ppb at high humidification (both electrodes RH 100%) and 0.6 V, which was enough to be used as the feed water for electrolysis. Very low concentration of platinum below 0.2 ppb was detected in the condensate discharged from the high humidification condition.